Example of how to use filters on your returns.

gistfile1.php

<?php

// Differentiate whether we need to load from
// cache or get live results.
function gdurl_googapi_cache($s){
        // First see if we have cached data (15 seconds?)
        $gdurl_transient = get_transient( 'gdurl_googapi_cache' );
 
        if( isset($gdurl_transient[$s]) ){
                return apply_filters(
                        __FUNCTION__, 
                        $gdurl_transient[$s]
                );
        }else{
                return apply_filters(
                        __FUNCTION__, 
                        gdurl_googapi_set_cache($s) 
                );
        }
}

?>